piss vs excreta

piss and excreta both are nouns.

Word	Noun	Adjective	Verb	Adverb
piss	Yes	No	Yes	No
excreta	Yes	No	No	No

As nouns, excreta is a hypernym of piss; that is, excreta is a word with a broader meaning than piss:

piss: liquid excretory product
excreta: waste matter (as urine or sweat but especially feces) discharged from the body

Other hypernyms of piss include body waste, excrement, excretion, excretory product.

piss (noun)	excreta (noun)
informal terms for urination	waste matter (as urine or sweat but especially feces) discharged from the body
liquid excretory product

piss (verb)	excreta (verb)
eliminate urine